1. Field of the Invention.
The present invention relates to gate valves and more particularly to multiple stage choke valves.
2. Description of the Prior Art.
Choke valves or flow restriction valves, as presently used and shown by the prior art, have generally comprised two or more disc members having transverse straight through or tapered openings which are partially or fully mated for controlling the flow volume and pressure drop across the flow restricting discs. These rotating disc type flow restriction valves operate satisfactorily but have the disadvantage of generating a surge of the fluid flow therethrough at the moment of opening or partially mating the flow-through apertures particularly when the pressure drop across the discs encompasses a wide range of pressure.
This invention is distinctive over flow restriction or choke valves of this type by providing a gate valve having a plurality of four flow restricting stages in its fluid passageway controlling the fluid flow by a series of radially spaced longitudinally staggered slots in its valve stem cooperating with a like series of fluid recesses formed in the flow passageway wall surrounding the gate valve stem.